This invention relates to devices for generating a swept clock frequency having a linear rate of change. More particularly, this invention relates to devices where the swept clock frequency is utilized to track a linearly changing time dependent variable where the value of the variable is known at only one point in time. Still more particularly, this invention relates to the provision of timing signals for causing successive measurements of a uniformly accelerating article to be made at equal and known increments in the motion of the article. Most particularly, this invention relates to the use of digital circuits to make a swept clock. In general, most devices have utilized analog circuits to generate a swept clock frequency. Such devices generally consist of a voltage controlled oscillator driven by a voltage which is ramped up or down at a predetermined rate in order to vary the frequency output of the oscillator. The degree of stability and accuracy of such circuits does not meet the requirements of certain applications. The present invention is designed to overcome these limitations by the use of digital circuits to generate a swept frequency.